optimal humidity inside chicken coop

Sep 20, 2017
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297
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Washington State
I keep hearing about the importance of keeping the coop dry inside, particularly for those of us living in cold winter climates. But, what is the optimal humidity? How humid is too humid?

I put a hygrometer inside our chicken coop recently, close to where the chickens roost, and the readings vary widely. For example, over the past 24 hours the lowest humidity reading was 16% and the highest reading was 80%. It read 78% when I opened up the coop at 8 am this morning.

My understanding is that there is a connection (although not always a direct or inverse correlation) between humidity and temperature. The temperature was a few degrees above freezing last night but has dipped a few degrees below freezing over the past couple of weeks and will dip below freezing again in the next several days.
 

EggSighted4Life

Crossing the Road
Apr 9, 2016
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California's Redwood Coast
When you are all closed up... the birds breath is putting humidity into the air.

If you have condensation on your windows or walls that's too much. And you need more ventilation. To me as long as there is NO condensation... it is low enough... BUT, I still have LOTS to learn! :pop

I live on the coast in the PNW... luckily we don't really freeze because our humidity is off the hook high... 65% in my house, and higher than that outside.
 

EggWalrus

Free Ranging
Aug 14, 2017
2,044
5,013
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Southeast Alabama
90% humidity here nearly all year long. We get a little break for a few months when it drops to around 70%. Our climate here is sub-tropical on the verge of being tropical. Winter is the only comfortable time.
 
Sep 20, 2017
255
297
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Washington State
If you have condensation on your windows or walls that's too much.
We do get some condensation on the coop window but my understanding is that condensation happens due to two factors: 1) humidity in the air, and 2) temperature difference between the air and the surface on which you might see drops.

So, when both the air and the glass in the coop window are warm, like in the summer, we never see condensation. In cooler weather, when the air exhaled by the birds is warm while the window pane is cold, we do begin to see condensation. I don't totally get the physics behind it but somehow moisture from the air is drawn to cold surfaces and settles on them.
 

Mrs. K

Free Ranging
10 Years
Nov 12, 2009
7,378
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western South Dakota
When the warm moist air reaches the cold surface, it rapidly cools, and the moisture condenses on the surface.

If you are seeing this, either your birds are too close to the surface or you don't have enough ventilation. We have been taught as children to shut things up to keep the warmth inside. Most of us hesitate to actually provide enough ventilation, thinking we are freezing the birds.

When I got enough ventilation, the movement of the air, pulls the moisture out of the coop, I quit seeing the condensation on the ceiling and walls, in an uninsulated coop. That is dry enough.

Mrs K
 
Sep 20, 2017
255
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Washington State
I'll have to think about ways to increase ventilation... our coop is already pretty "holey." There are (screened in) slits on opposing walls just under the ceiling, and the door is not at all tight. There is probably a half inch wide gap running from top to bottom along the edge of the door where it opens, and smaller gaps between the planks that the door is made of. We also drilled a bunch of small holes in the wall of the coop near the roost. What else can we do?
 

Folly's place

Crossing the Road
8 Years
Sep 13, 2011
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southern Michigan
Pictures of your coop will help, but if there's condensation inside, it's too wet, and underventilated. (That's not really a word!) Talking about 'drilling holes' sounds totally inadequate; it's more about having hardware cloth covered openings, window sized.
You can't make it dryer than the ambient humidity, but it shouldn't be damper.
Mary
 

aart

Chicken Juggler!
Premium member
7 Years
Nov 27, 2012
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My Coop
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Optimal humidity inside coop would be...less than outside,
cause ya can't make it drier inside coop than it is outside,
unless you button up coop and install an HVAC system.

Yes, warmer air holds more moisture, I can't explain the physic either.

My coop is pretty well ventilated, and I have a closed waterer and remove poops daily.
But this year we had a huge thaw in January, after tons of snow and cold, and I had dripping condensation on underside of north shed roof(which is 1x boards, tar paper, and asphalt shingles)... that roof had a good foot of snow on it keeping it cold.

upload_2018-10-29_6-54-9.png
 

Egghead_Jr

Crowing
9 Years
Oct 16, 2010
7,044
2,775
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NEK, VT
I keep hearing about the importance of keeping the coop dry inside, particularly for those of us living in cold winter climates. But, what is the optimal humidity? How humid is too humid?

I put a hygrometer inside our chicken coop recently, close to where the chickens roost, and the readings vary widely. For example, over the past 24 hours the lowest humidity reading was 16% and the highest reading was 80%. It read 78% when I opened up the coop at 8 am this morning.

My understanding is that there is a connection (although not always a direct or inverse correlation) between humidity and temperature. The temperature was a few degrees above freezing last night but has dipped a few degrees below freezing over the past couple of weeks and will dip below freezing again in the next several days.
You have high readings in the morning. This is due to the bids being in coop all night. What causes high humidity is the birds breathing and pooping all night. It's this stale moist air you want to vent out.

A little condensation on a window is nothing to worry about. Condensation on ceiling or running down walls is major concern. Windows are so thin and we typically don't use double insulated glass in coops. A little condensation on a window is quite normal, water running down it is too much.

Placement of venting is key. You don't want wind on the birds. If your roof pitch is more than 4/12 then vents on low end and high end eaves is plenty. If a gable then both eaves and both gable ends. Think about this, what you're doing is letting fresh air in low end, a natural vacuum is created with hot coop air moving out high vents, this moves a lot more air than the size of vent would passively. The natural vacuum moves air like using a fan to outlet would. Fresh air is sucked in, mixes with wet coop air along roof line and is pushed out top vents. All we are doing is moving out the moisture without drafting the birds. Keep roosts over a foot away for level of low inlet vents.
 
Sep 20, 2017
255
297
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Washington State
Thanks all! This is a really great discussion. I've been slow to jump back in as I keep reminding myself to take pictures of the coop and then forgetting.

To answer some questions, here is what ventilation looks like currently in our coop:

We have vents on the low end and high end eaves, I'd estimate 2-3 inches wide and running the entire length of the coop, hardware cloth covered. And, as I wrote earlier, the door is made up of slats that do not join tightly together, plus there is probably a half-inch gap between the door and the wall on one side. (Air coming in through the door will not blow on the birds.) We do also have a large window (double-paned but I'm not sure if it's insulated) which is closed at night.

During the day there is plenty of ventilation even in the winter, as we open the main door, the window, and the little trap door that serves as a ramp to the covered run. What I'm really concerned with is whether we have adequate ventilation for winter nights, to avoid frostbite.
 

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